Desulfurizing agent and its preparation



Patented Mar. 11, 1952 UNITED STATES PATENT OFFICE",

DESULFURIZDV G AGENT ANDITS- PREPARATION' Elwood B; Backensto,,Woodbury,LN. J., assignor; to Socony-Vacuum- Oil Company, Incorporated, acorporation of NewYork NoDrawing; Application October 2, 1947, SeriaLNo. 777,600

9 Claimsr (Cl. 252192) The presentinvention relates tothe removal of free sulfur. and .organicsulfhydryls'from, hy:-'

more than twocarbon atoms for the systemloilaqueous alkaline solution did. not favor practical extraction of thehigher. molecular weight sulfhydryls zfrom the: hydrocarbon mixtures. deficiency later was overcome byadding to the aqueous alkaline solution a substance, generally known in the art as a solutizer; which enhanced the capacity of aqueous alkaline solutions for exe tracting sulfhydryls from hydrocarbon mixtures; or, in other words, an'aqueous alkalinesolutionl containing a soluti-zer has apartitioncoefficientx. for sulfhydryls in the system oil-aqueous alkaline; solution of a solutizer favoringpractical extraction ofthe-sulfhydryls the oil by the aqueous alkaline solution. The partition coefficient for sulfhydryls in the system oil containing 'sulfhydryls-aqueous alkali metal hydroxide'containing solutizer is'known generally in the art as the Kq value. The" Kq valueristhesratio oh the concentration of the sulfhydryl in the aqueous phase to the concentration-ofthe sulfhydryl in the hydrocarbonphase'.

Many compounds have founduse" to agreater or lesser extent-as;solutizers.. Two compounds in particular have received particular attention, to wit: isobutyric acid and alkyl phenols; Of? the two the .latter'is more commonly used because the alkyl phenols are present in the products of" cracking of hydrocarbons; particularly mineral oil. The alkyl phenols are used in an' aqueous solution of alkali metal hydroxide; th'echoicebe tween sodium hydroxide and'potassiumhydrox' ide generally being, dependentupon economic factors as well as, the limit of solubility of the alkyl phenolates. Generally; the aqu'eoussolution of alkali metal hydroxide is4.0 normal to" 6.0 normal to alkalimetal hydroxide and 1.0 normal to 3.0 normal to alkali metalalkyl'phenolate" when using potassium hydroxide 'andthe potassium alkyl phenolates; and SLOhormal' to- 5":0-"normal to alkali metal hydroxide and 1.0 normal to" 2.0 normal to alkali metal alkyl phenolate when using sodium hydroxide.

This I In general, the removal of'sulfhydrylsfirom;

hydrocarbon mixtures or from mineral oil disetillates comprises contacting the-hydrocarbon mixture containing alkyl and or aryl sulfhydrylsi:

i. e. mercaptans: and/or thiophenols with an:

aqueous 1 alkaline solution containing: a: solutizer,

The' aqueous solution containingithe extractedsulfhydryls andysolutizer. iscseparatedvfrom the hydrocarbon mixture andthe fouled solutizensolutionregeneratedr Regeneration 'of the fouled-i aqueous: solution may be accomplished; in either of two operations. The fouled aqueous solut-ioni maybe steamed and the sulfhydryls thus-vapor ized or entrained in? the steam orthesulfhydryls, may be-oxidizedto disulfides WlthaOXYgBll in1the= presence of' a catalyst such i as-the sulfidess of cation Serial Number. 490,490these'inventorshave r disclosed aprocess whereingasoline-or other light hydrocarbon fraction containing mercaptanz-sulw fur is contacted with a-caustic alkali-reagent of th'etype normally; used'for'the removal'oof mer-- captan sulfur and the reagentcontaining;mercaptans is then separated;vfronr the treatece=oil.. The reagent containing mercaptans is regenerated by blowing gas containing free oxygen therethrough in the presence of a phenolic oxidation promoter such as thez-polyhydroxybenzenes, hydroquinone and. pyrogallol. Inapplication Se-.- rialNumber 490,491 the same inventorsihave dis-1 v closed a similar process .in which the alkaline re. agent containing. mercaptans is regenerated lby v blowing-r gas containing 7 free oxygen th'ereth'roughl in the presence, of polyhydroxybenzene.carboxylic acids and derivatives thereoflsuch' as protolcatechuic acid, gallic acid; tannic acid andQthe like and various tannin materials' derived from, oak-bark, quinine-bark, coffee, moringnetannin,- cutch, chestnut, logWood,-. sumac-and other natural sources of suchitannin materials.. After-megeneration, the aqueous alkaline solution containing the solutizer or solutizersris-readyioreusein: the treatment of furtheramounts; of: hydrocarbun-mixtures containingzsulfhydrylsw The treatment of some hydrocarbon =dis-til-rlates, particularly some mineral oil distillates, involves the removal of free sulfur. In the past this has been achieved tothe greater or lesser satisfaction of the refiner by contacting the hydrocarbon mixture containing the free sulfur with aqueous solutions of alkali metal polysulfides in a manner similar to that employed in extracting sulfhydryls. However, with this difference the polysulfide solution is not readily regenerated.

Thus, when it has been necessary to remove free sulfur as well as sulihydryls from hydrocarbon it has been necessary to use two separate and distinct extraction media. It has now been discovered that an aqueous alkaline solution of the novel solutizer can be used not only to extract sulfhydryls but also to extract free sulfur from hydrocarbon mixtures.

The novel solutizer is that portion of the byproduct tar obtained in the production of thiophene as described in application for United States Letters Patent Serial No. 693,176, filed August 27, 1946, in the names of Rowland C. Hansford, Herbert G. Rasmussen and Alexander N. Sachanen (now U. S. Patent Number 2,450,-' 659) which is soluble in aqueous alkali metal hydroxide solution. As described in' this copending application, sulfur and one or more normal C4 aliphatic hydrocarbons are separately heated to temperatures such that combining the preheated sulfur and preheated hydrocarbon material will give a mixture having a temperature in excess of about 850 F. The preheated reactants are mixed and the temperature of the mixture maintained in excess of about 850 F. for a period of time sufficient to produce the desired products. Thereafter the temperature of the mixture is reduced to less than about 850 F. With the exception of hydrogen sulfide and a tar, thiophene or butadiene are the principal compounds obtained. The novel solutizer is obtained from the aforesaid tar.

One form of the novel solutizer is obtained by extracting the aforesaid b'y-product tar with 30% aqueous alkali metal hydroxide solution. Another method of obtaining the novel solutizer comprises steam distilling the aforesaid by--product or thiophene tar and subjecting the steam distillate to vacuum distillation. The fraction boiling between 107 F. an absolute pressure of millimeters of mercury to 127 F. an absolute pressure of 10 millimeters of mercury contains-the solutizer. This fraction has a major constituent thiophene-3-thiol,

A further method comprises allowing the thiophene tar to age and steam distilling the aged thiophene tar to obtain a product that is about 90% caustic soluble. It is characteristic of this latter method that the quantity of liquid product is less than that from fresh tar and that the distillate contains less thiophehe-B-thiol. On the other hand, the distillate from "aged thiophene tar is markedly superior to thiophene-3- thiol as a solutizer for sulfhydryls.

Several explanations for this apparent anomaly are possible. One may be suggested without in any way limiting the scope of this invention. It has been determined that a trithiocompound is also present in the thiophene tar. On the basis of knowledge presently available, the formula s=oc=s (dithiothiophane or 3,4-thiolanedithione) has been assigned to this trithiocompound. This compound is soluble in aqueous caustic when heated at 100 to 212 F. for some time with aqueous caustic solution containing 20 weight per cent sodium hydroxide. It appears possible that the trithiocompound is enolized by the treatment at elevated temperatures in the aqueous caustic solution to a compound with weakly acidic hydrogen atoms which is a better solutizer than thiophene-3-thiol:

At this time it is to be noted that aged thiophene tar is the aforesaid by-product thiophene tar which has been allowed to stand at atmospheric conditions for several weeks. A steam distillation of the thiophene tar apparently results in some type of steam pyrolysis, for a large amount of thiophene-thiol is obtained on steam distilling a fresh thiophene tar, i. e. after immediate recovery from the process producing it. However, after allowing the tar to stand at atmospheric conditions for several Weeks before steam distillation, the yield is much smaller and the product obtained contains only a small amount of thiophene-thiol.

As was pointed out hereinbefore, a satisfactory means for determining the solutizer value of a compound is to determine the Kq value of an aqueous solution of the compound for a sulfhydryl dissolved in a hydrocarbon. The Kq value of three forms of the novel solutizer was determined for normal butyl mercaptan dissolved in isooctane. The Kq value of two standard solutizer solutions for normal butyl mercaptan was determined under the same conditions. The data thus obtained are given in the appended table.

solutizer solution I An aqueous solution 4 normal to potassium hydroxide (KOH) and 2 normal to the steam distillate of aged thiophene tar on the basis of a molecular weight of 116 for the solutizing constituents of the tar and that per cent of the distillate is soluble in the aqueous caustic solution.

solutizer solution III (4N KOH-2N KCr) An aqueous solution 6 normal to potassium hydroxide (KOH) and 2 normal to potassium alkyl phenolate (potassium salt of metacresol) solutizer solution III (4N KOH--2N Kcr) An aqueous solution 4 normal to potassium hydroxide (KOH) and 2 normal to potassium alkyl phenolate (potassium salt of metacresol).

Solutz'zer solution IV An aqueous solution 4 normal to potassium hydroxide (KOH) and 2 normal to the fraction of steam distillate of fresh thiophene tar boiling at 127-168" F. at a pressure of 10 millimeters of mercury on the basis of a molecular weight of 130 and that only 42 per cent of the fraction is soluble in the alkaline solution.

Solutz'ze-r solution V An aqueous solution 4 normal to potassium hydroxide (KOH) and 2 normal to thiophene-3- thiol obtained by vacuum distillation of steam distillate of fresh thiophene tar; per cent thiophene-3-thiol.

The Kq values at equilibrium for the solutizer solutions enumerated hereinbefore were obtained by mechanically agitating isooctane containing normal butyl mercaptan in a closed container for one hourat a treating rati'o of- 051' at room temperature-under an atmosphere of nitrogen:

(II), isisuperior to 4N KOH'--2N KCr (111). asa solutizer. These data also establish that'ai 4N KOH solution containing'suflicient' of the steam distillate of agedthiophene;.tar" to make the solution2 normal theretov (Ilisequivalent to the SN KOH-2NJKCf. (II). and superior touthe 4N KOH-l-QN'KCr (111) as asolutizer These data also establish .thatssolutizer Solutions lv and V are equivalent in solutizing power' and; whileof approximately one-half the solutizing, power of 4N KOH-2N KCr have useful solutizing powers.

The ability of the novel solutizer to extract free sulfur from hydrocarbon solutions of the same is demonstrated by the following.

A 30 weight per cent solution of sodium hydroxide (NaOH) of crude aged thiophene tar (approximately 15% by volume includin the caustic insoluble material) when agitated for five minutes with an equal volume of isooctane containing 6 parts per million of free sulphur (of the order of free sulfur concentration in petroleum distillates) reduced the free sulfur content of the isooctane to one part per million as shown by the nitroprusside fading time.

It is to be understood, as is generally known to those skilled in the art, that aqueous solutions of sodium hydroxide may be used. Accordingly, the use of aqueous solutions 1.0 normal to 6.0 normal to sodium hydroxide and containing an effective amount of the novel solutizer is within the purview of the present invention. It is also to be understood that the present invention is not limited to thiophene-3-thiol or the trithiocompound described hereinbefore but includes the homologues of thiophene-3-thiol, the trithiocompounds of fresh or aged thiophene tar as well as derivative and polymers of the foregoing and condensation products with other constit uents of the thiophene tar or, in general, that portion of thiophene tar, fresh or aged, which is soluble in an aqueous solution of alkali metal hydroxide containing about 5 weight per cent to about 40 weight per cent of alkali metal hydroxide.

I claim:

1. A method for producing material suitable for use as a solutizer in the removal of sulfhydryls from admixture with hydrocarbons which comprises separately preheating sulfur and a Cir-hydrocarbon selected from the group consisting of normal butane, normal butenes and butadienes, to a temperature such that combining said sulfur and said hydrocarbon will give a reaction mixture having a temperature between 850 F. and about 1400 F.; mixing the preheated sulfur and the preheated hydrocarbon; reacting said preheated sulfur and said preheated hydrocarbon at a reaction temperature varying between 850 F. and about 1400 F. to yield a mixture containing a thiophene tar; im-

mediately; reducingr the; temperature v of; the mixture containing said tar" to a temperature:- less :than 850 F5, separating: the tarfrom-said mixture; treating said tarto :obtain a fraction-=- solublein aqueous about 5t0 about '40'zweight per" cent' alkali metal hydroxide and a fractionin soluble-in: said aqueous alkali metal hydroxide and separating said soluble fraction from said" insoluble fraction.-

2; The-methodfor-producing material suit-. able=-for use as 'asolutizerintheremoval-of sulf-'- hydryls from admixture-with hydrocarbons as described andset forth in'claim lwherein the separated; tar is 'subj ected to steam distillation and a fraction of the steam distillate boiling at about 127 to about 168 F. at an absolute pressure-of 10 "millimeters of'mercury separated.-

3. The method for producingmaterialsuitable' for use asasolutizer in' the-removal of sulfhy dryls from admixture with hydrocarbons as describedand set forth in1claim- 1 wherein thesBDaxrated tar-is contactedwith an-aqueoussolutioncontaining about 20 to about 30 weight-percent alkali metal hydroxide and a fraction soluble in an aqueous solution containing about 5 to about 40 weight per cent alkali metal hydroxide separated from a fraction insoluble in said aqueous about 5 to about 40 weight per cent alkali metal hydroxide.

4. A solution for the extraction of free sulfur and sulfhydryls from hydrocarbon fluids which comprises an aqueous alkaline solution to which has been added a water-insoluble fraction of the steam distillate of thiophene tar in amount effective to increase the capability of said aqueous alkaline solution to dissolve sulfhydryls, said fraction of said steam distillate having a boiling range of about 127 to about 168 F. at an absolute pressure of 10 millimeters of mercury; said thiophene tar having been obtained by separately preheating sulfur and a C4-hydrocarbon selected from the group consisting of normal butane, normal butenes and butadienes to a temperature such that combining said sulfur and said hydrocarbon will give a reaction mixture having a temperature varying between about 850 F. and about 1400 F., mixing the preheated sulfur and the preheated hydrocarbon, reacting said preheated 'sulfur and said preheated hydrocarbon at a reaction temperature varying betweent 850 F. and about 1400 F. to yield a mixture containing a thiophene tar, immediately reducing the temperature of said mixture containing said thiophene tar to a temperature of less than 850 F., and separating said tar from said mixture.

5. A solution for the extraction of free sulfur and sulfhydryls from hydrocarbon fluids as set forth and described in claim 4, wherein the steam distillate is derived from aged thiophene tar.

6. A solution for the extraction of free sulfur and sulfhydryls from hydrocarbon fluids as set forth and described in claim 4, wherein the steam distillate is derived from fresh thiophene tar.

7. A solution for the extraction of free sulfur and sulfhydryls from hydrocarbon fluids which comprises an aqueous alkaline solution to which has been added a fraction of thiophene tar in amount effective to increase the capability of said aqueous alkaline solution to dissolve sulfhydryls, said fraction of thiophene tar being soluble in aqueous solutions containing about 5 to about 40 weight per cent of alkali metal hydroxide, said thiophene tar having been obtained 7 by separately preheating sulfur and a Cir-hydrocarbon selected from the group consisting of nor-c mal butane, normal butenes and butadienes to a temperature such that combining said sulfur and. said hydrocarbon will give a reaction mixture having a temperature varying between about 850 F. and about 1400 F., mixing the preheated sulfur and the preheated hydrocarbon, reacting said preheated sulfur and said preheated hydrocarbon at a reaction temperature varying between 850 F. and about 1400 F. to yield a mixture containing a thiophene tar, immediately reducing the temperature of said mixture containalkali metal hydroxide 'is derived from aged thiophene tar.

4 9. A solution'for the extraction of free sulfur and sulfhydryls from hydrocarbon fluids as set forth and described in claim 7, wherein the fraction of thiophene tar soluble in aqueous solutions containing about 5 to about 40 weight per cent of alkali metal hydroxide is derived from fresh thiophene tar.

' ELWOOD B. BACKENSTO.

REFERENCES CITED The following references are of record in the file of this patent:

V UNITED STATES PATENTS Number OTHER REFERENCES Steinkopf: Die Chemie des Thiophens, pp. 62, 63, 100. Edwards Lithoprint, 1944.

Morton: The Chemistry of Heterocyclic Com'-' pounds, pp. 43, 44, McGraw-Hill, N. Y., 1946. 

4. A SOLUTION FOR THE EXTRACTION OF FREE SULFUR AND SULFHYDRYLS FROM HYDROCARBON FLUIDS WHICH COMPRISES AN AQUEOUS ALKALINE SOLUTION TO WHICH HAS BEEN ADDED A WATER INSOLUBLE FRACTION OF THE STEAM DISTILLATE OF THIOPHENE TAR IN AMOUNT EFFECTIVE TO INCREASE THE CAPABILITY OF SAID AQUEOUS ALKALINE SOLUTION TO DISSOLVE SULFHYDRYLS, SAID FRACTION OF SAID STEAM DISTILLATE HAVING A BOILING RANGE OF ABOUT 127* TO ABOUT 168* F. AT AN ABSOLUTE PRESSURE OF 10 MILLIMETERS OF MERCURY; SAID THIOPHENE TAR HAVING BEEN OBTAINED BY SEPARATELY PREHEATING SULFUR AND A C4-HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF NORMAL BUTANE, NORMAL BUTENES AND BUTADIENES TO A TEMPERATURE SUCH THAT COMBINING SAID SULFUR AND SAID HYDROCARBON WILL GIVE A REACTION MIXTURE HAVING A TEMPERATURE VARYING BETWEEN ABOUT 850* F. AND ABOUT 1400* F., MIXING THE PREHEATED SULFUR AND THE PREHEATED HYDROCARBON, REACTING SAID PREHEATED SULFUR AND SAID PREHEATED HYDROCARBON AT A REACTION TEMPERATURE VARYING BETWEEN 850* F. AND ABOUT 1400* F. TO YIELD A MIXTURE CONTAINING A THIOPENE TAR, IMMEDIATELY REDUCING THE TEMPERATURE OF SAID MIXTURE CONTAINING SAID THIOPENE TAR TO A TEMPERATURE OF LESS THAN 850* F., AND SEPARATING SAID TAR FROM SAID MIXTURE. 